Question

All are histological features of monocytes and macrophages except? a. Large, irregularly shaped cells with a kidney-shaped or round nucleus. b. Ample cytoplasm in contrast to lymphocytes c. Smooth surface d. Differentiated cells commonly bear microvilli that are visualized with localization of vimentin e. After activation cells revert to an activated state and appear amoeboid in nature

Short answer

a) Large, irregularly shaped cells with a kidney-shaped or round nucleus b) Ample cytoplasm in contrast to lymphocytes c) Smooth surface d) Differentiated cells commonly bear microvilli that are visualized with localization of vimentin e) After activation cells revert to an activated state and appear amoeboid in nature Answer: c) Smooth surface

Step-by-step solution

Option a: Large, irregularly shaped cells with a kidney-shaped or round nucleus

Monocytes and macrophages are indeed large, irregularly shaped cells with a kidney-shaped or round nucleus. They are larger than many other white blood cells and have an irregular shape that helps them perform their immune functions. Therefore, this option describes a feature of monocytes and macrophages.

Option b: Ample cytoplasm in contrast to lymphocytes

Monocytes and macrophages have ample cytoplasm, which is used for various functions such as phagocytosis and enzyme production. This feature distinguishes them from lymphocytes, which have a smaller amount of cytoplasm. Hence, this option also describes a histological feature of monocytes and macrophages.

Option c: Smooth surface

Monocytes and macrophages do not have a smooth surface. In fact, they usually have a rough, irregular surface due to the presence of various processes, such as pseudopodia and microvilli. This allows them to interact with their environment and perform their immune functions more effectively. Thus, this option does not describe a feature of monocytes and macrophages and is the correct answer.

Option d: Differentiated cells commonly bear microvilli that are visualized with localization of vimentin

Differentiated monocytes and macrophages commonly have microvilli on their surface, which can be visualized using localization of vimentin, an intermediate filament protein. These microvilli increase the cell surface area and facilitate interactions with other cells and particles in their environment. Therefore, this option describes a feature of monocytes and macrophages.

Option e: After activation cells revert to an activated state and appear amoeboid in nature

When monocytes and macrophages become activated, they can assume an amoeboid shape which makes them more mobile and allows them to move towards the site of infection or inflammation. This is an essential feature of these cells, as they need to be able to migrate to perform their immune functions. Thus, this option also describes a histological feature of monocytes and macrophages. In conclusion, the correct answer is option c (smooth surface), as it is not a histological feature of monocytes and macrophages.

Key concepts

Immune Cell Morphology

Understanding the morphology, or shape, of immune cells is crucial in the world of histology and immunology. Monocytes and macrophages, key players in our immune system, have distinct characteristics that enable them to effectively carry out their roles. Monocytes are identified by their large size and irregular shapes, often described as having a kidney-shaped or round nucleus. Their ample cytoplasm sets them apart from lymphocytes, which are known for having less cytoplasm.

Upon reaching an inflammation site, monocytes differentiate into macrophages, which can vary in appearance based on their environment and activation state. Macrophages maintain the irregular morphology but are generally larger and exhibit visceral features enabling them to efficiently phagocytize pathogens and cellular debris. An easily overlooked but crucial aspect of monocyte and macrophage functionality is their morphology, providing visual cues to their ability to navigate and interact within different biological contexts.

Amoeboid Activation State

The term 'amoeboid activation state' refers to a transformation that immune cells undergo, specifically monocytes and macrophages, allowing them to respond to inflammation or infection. Initially, these cells present a somewhat spherical or irregular shape. However, upon activation, they adopt an amoeboid form, reminiscent of an amoeba, with dynamic and extending pseudopods. This metamorphosis is fascinating as monocytes and macrophages transition from a passive to a highly motile state.

This change is vital for them to traverse the endothelium, squeeze through the tissue matrix, and reach the site of infection or damage. The term 'amoeboid' highlights the cells' flexible shape and their ability to maneuver through narrow spaces, adhere to various surfaces, and engulf foreign particles through phagocytosis. The amoeboid activation state is, therefore, a testament to the plasticity and adaptive nature of these immune cells.

Microvilli and Vimentin Localization

Microvilli are minute, finger-like projections that can be found on the surface of differentiated monocytes and macrophages. These structures play an instrumental role in enhancing the surface area of these immune cells, which facilitates the detection of pathogens and cell debris. The presence of microvilli, along with the flexible amoeboid state, is indicative of the readiness of macrophages to perform their immune surveillance duties.

The protein vimentin, which is part of the cytoskeleton, can be seen localized in these cells as well. Vimentin is not just a structural component; it is involved in a myriad of cellular functions, including cell integrity maintenance, adhesion, and migration. Histological staining techniques enable vimentin localization visualization, helping to differentiate between microvilli-bearing cells like macrophages, and other cell types. Precise knowledge of vimentin localization and microvilli distribution is indispensable for understanding the behavior and functionality of these dynamic immune cells.